pod2docbook converts files from pod format (see perlpod) to DocBook 4.2 SGML (see http://www.docbook.org/).
The program itself is merely a driver for the Pod::2::DocBook class; if you're interested in details of pod-to-SGML translation see Pod::2::DocBook.

Alligator Descartes <descarte@symbolstone.org> wrote a module called Pod::2::DocBook,
which was later maintained by Jan Iven <jan.iven@cern.ch>.
That module was based on the original pod2html by Tom Christiansen <tchrist@mox.perl.com>.